Overnight Intensive Recovery: Elective Open Aortic Surgery Without a Routine ICU Bed

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1 Eur J Vasc Endovasc Surg 30, (2005) doi: /j.ejvs , available online at on Overnight Intensive Recovery: Elective Open Aortic Surgery Without a Routine ICU Bed C.J. Callaghan, 1 A.G. Lynch, 2 I. Amin, 1 M. Fazel, 1 M.J. Lindop, 3 M.E. Gaunt 1 and K. Varty 1 * 1 Cambridge Vascular Unit, Addenbrooke s Hospital, Cambridge CB2 2QQ, Departments of 2 Public Health and Primary Care, Centre for Applied Medical Statistics, University of Cambridge, Robinson Way, Cambridge CB2 2SR, and 3 Anaesthesia, Addenbrooke s Hospital, Cambridge CB2 2QQ, UK Objectives. Most patients are managed on the intensive care unit (ICU) after elective open aortic surgery. We preoperatively identify patients suitable for extubation in theatre with overnight management in theatre recovery before discharge back to the ward (overnight intensive recovery (OIR)). The safety of this was investigated. Design. Retrospective case note analysis of all patients who underwent EOAS from 1998 to 2002, recording in-hospital morbidity and mortality. Physiological and operative severity score for the enumeration of mortality and morbidity (POSSUM) data were collected prospectively. Methods. Patients were divided into those selected for OIR and those booked for elective ICU admission. Observed morbidity and mortality data were compared with predicted outcomes generated by Portsmouth-POSSUM and POSSUM equations. Results. Hundred and fifty-two out of 178 patients used OIR; 155 patients had abdominal aortic aneurysm (AAA) repair. The elective ICU group had significantly higher anaesthetic risk scores (ASA grade), larger AAA, greater intraoperative blood loss and longer operations. In the OIR group, ten patients (7%) needed ICU admission within 48 h postoperatively. Complications occurred in 85/152, with two deaths. There was no excess morbidity or mortality in the OIR group (predicted 95% CI and 5 17, respectively). Conclusion. Most patients having elective open aortic surgery can be managed safely using OIR. Keywords: Abdominal aortic aneurysm; Arterial occlusive diseases; Recovery room; In-hospital mortality. Introduction The majority of vascular surgeons in the UK routinely admit patients to an intensive care unit (ICU) after elective open aortic surgery. 1 Admission to ICU enables extubation after warming and fluid replacement as well as invasive monitoring and intensive assessment under close medical supervision. However, with advances in anaesthetic techniques, extubation in theatre after elective open infrarenal abdominal aortic aneurysm (AAA) repair has been shown to be safe. 2 Others have demonstrated that routine admission to ICU after infrarenal aortic surgery is unnecessary by identifying appropriate patients either at the end of surgery, 3 or following observation in theatre recovery. 4 *Corresponding author. Mr K Varty, Consultant Vascular Surgeon, Department of Surgery, Box 201, Addenbrooke s Hospital, Hills Road, Cambridge CB2 2QQ, UK. address: kevin.varty@addenbrookes.nhs.uk These approaches have the disadvantage that an ICU bed is required to be available until after the operation has been completed, or later. This could be avoided by preoperatively identifying patients suitable for management without ICU admission. In the mid-1990s our institution introduced a system by which a proportion of patients having major elective abdominal surgery (e.g. open infrarenal aortic surgery, Whipple s pancreaticoduodenectomy, hemihepatectomy) were preoperatively selected for extubation in theatre and management overnight in theatre recovery without a back-up ICU bed. This is known as the overnight intensive recovery (OIR) pathway. With the establishment of a specialist vascular unit in 1998, indications for OIR were extended to include suitable patients undergoing juxta- and suprarenal aortic surgery. The introduction of non-icu pathways for selected patients would be expected to reduce costs, free ICU beds for emergency admissions, and reduce / $35.00/0 q 2005 Elsevier Ltd. All rights reserved.

2 Is Routine ICU Necessary after Elective Open Aortic Surgery? 253 cancellations of elective surgery due to unavailability of ICU beds. However, the priority is to determine the safety of these approaches. We performed a retrospective study to measure in-hospital morbidity and mortality, and, using physiological and operative severity score for the enumeration of mortality and morbidity (POSSUM) equations to generate predicted morbidity and mortality, we compared observed and predicted outcomes. Methods All patients undergoing elective open aortic surgery at the Cambridge Vascular Unit between 1st January 1998 and 31st December 2002 were included in the study. Contraindications to offering surgery are a combination of: age O85 years, severe cardiorespiratory or renal compromise, dementia, bed-bound state, and malignancy with!2 years life expectancy. Patients who had surgery were identified using a combination of computerised theatre records, surgeons logbooks, and theatre booking diaries. POS- SUM variables were collected prospectively. Case notes were analysed retrospectively for observed inhospital morbidity and mortality. Patients were excluded from the study if their case notes were missing. OIR pathway Patients that accept an offer of surgery are assessed preoperatively by a consultant vascular surgeon and consultant anaesthetist including clinical assessment along with routine electrocardiography, chest radiography, and blood tests (full blood count, urea and electrolytes, coagulation screen). Transthoracic echocardiography is not used routinely, but is reserved for patients with significant ischaemic heart disease, suspected valvular heart disease, or if exercise tolerance was unable to be assessed clinically. If further preoperative assessment is required, the patient is referred to an appropriate specialist. To enable accurate operative planning, all patients with AAA have contrast-enhanced spiral CT scanning, and those with aortic occlusive disease (AOD) undergo intraarterial angiography. Preoperative review of these investigations leads to a joint decision regarding suitability for OIR. Contraindications to the use of OIR were: significantly impaired renal function, technically difficult and/or prolonged surgery expected, poor exercise tolerance, or likelihood of requiring postoperative ventilation. Patients not appropriate for OIR are booked for an elective postoperative ICU bed. Surgery on patients using OIR proceeds despite full occupancy of ICU beds. The OIR area is located in theatre recovery and is staffed at a nurse to patient ratio of 1:1. A booking service is run to ensure availability. The maximum stay is 24 h, after which patients must move to a surgical ward or be referred to ICU for admission. OIR beds cannot be used by overflow patients from ICU, ward patients, or those having emergency surgery. There are no facilities for mechanical ventilation or renal replacement therapy. Overnight medical care is provided by the on-call anaesthetic and general surgical teams. After review in the morning by the vascular surgery team, stable patients are discharged to the surgical ward, where the nurse to patient ratio is 1:7. Indications for ICU are: haemodynamic instability requiring ongoing invasive blood pressure monitoring, deteriorating respiratory or renal function, or if discharge to the ward was deemed unsuitable by the surgeon or anaesthetist for any other reason. Epidural and central venous catheters are managed on the ward, but radial artery catheters are removed before transfer. Surgical technique Access to the abdominal aorta is via a midline incision with a transperitoneal approach. Endoaneurysmal AAA repair, aortic bypass and endarterectomy are performed using standard techniques. Intravenous heparin is given according to the surgeons preference, but is typically 5000 IU. Anaesthetic technique General anaesthesia is used with intensive monitoring using radial artery and central venous catheters, and an oesophageal temperature probe. Continuous epidural analgesia is established with a mid-thoracic catheter. Pulmonary artery catheterisation is not used routinely. Active warming with a warm air blanket and fluid warmer is used to ensure that the patient s temperature at the completion of surgery is at least 36 8C. Ultra short-acting drugs such as remifentanil and atracurium are used to ensure that no drug action persists into the postoperative period and to facilitate extubation in theatre. Paracetamol, oral or rectal, is an adjunct to epidural analgesia.

3 254 C. J. Callaghan et al. POSSUM POSSUM is a scoring system that collects 12 preoperative and six intraoperative variables to generate a physiological score (PS) and operative score (OS), respectively. 5 Logistic regression analysis yielded separate equations for predicted morbidity and mortality, both using the PS and OS scores. POSSUM defines morbidity as the presence of one or more complications. Expected morbidity for our patient population was generated using the POSSUM morbidity equation, 5 as validated for vascular surgery. 6 The Portsmouth modification to the POSSUM mortality equation (P-POSSUM) was developed after the POSSUM mortality equation had been shown to overestimate mortality. 7 Expected mortality was therefore calculated using the P-POSSUM mortality predictor equation for general surgery, 7 as this has been shown to model elective AAA surgery mortality accurately. 8 Statistical methods Patients were divided into two groups on the basis of the preoperative decision to manage the patient in either OIR or ICU postoperatively. Continuous variables are summarized as the median with interquartile range (IQR). Categorical variables are expressed as a whole number with percentage; those with more than two categories (e.g. New York Heart Association (NYHA) score) are summarized as frequencies for each category. The two groups were compared using the Mann Whitney test for continuous variables and Fisher s exact test for categorical variables. Postoperative and ICU stay were expressed as mean and standard deviation (SD). Comparison was with a two-tailed t- test. For all tests, significance was defined as p! Statistical analysis was performed using SPSS software version 11.0 (SPSS Inc., Chicago, IL, USA). P-POSSUM data were analysed as follows. For each patient, the probability of morbidity and the probability of mortality were calculated using POSSUM and P-POSSUM equations, respectively. We investigated the distribution of the total number of patients experiencing complications, or the total number of deaths, conditional on this set of probabilities. This conditional distribution was investigated using the freely available software package WinBUGS. 9 Rather than the point estimates of other approaches, 10 we can investigate the 95% confidence intervals (CI) for the number of patients predicted to die or to have complications. The code for use in WinBUGS is available from AGL s website ( uk/cams/andy/programs.htm). Missing P-POSSUM variables were recorded as the lowest scoring option to ensure that predicted morbidity and mortality outcomes were not overestimated. 11 Results A total of 181 patients were identified. Three were excluded due to missing case notes but these patients were all alive at discharge. Of the patients included in the study, 152 patients had been preoperatively selected for OIR and 26 were booked for elective postoperative ICU. Indications for elective ICU admission were: difficult or prolonged surgery expected one patient; difficult or prolonged surgery expected in a patient with significant cardiac, respiratory or renal dysfunction six patients; significant cardiac, respiratory or renal dysfunction alone or in combination 19 patients. Patient demographics and co-morbidities The median age for all patients was 72 years (66 77) (Table 1). Patients in the elective ICU group had a higher rate of co-morbidities and were more likely to have a history of angina, with larger aneurysms, higher ASA, NYHA, and POSSUM physiology scores, and poorer left ventricular function on echocardiography. Surgical procedures and intraoperative variables AAA repair was performed in 87% (155/178) of cases (tube grafts 83 patients, trouser grafts 69 patients, data missing three patients). Infrarenal AAA repairs made up the majority of cases in both groups, with infrarenal aortic bypass for AOD and juxtarenal AAA repairs the second and third most common procedures, respectively (Table 2). Both patients with suprarenal AAA were managed using OIR. Patients in the elective ICU group had higher blood loss and longer operative times (Table 3). Twenty-four patients had missing blood loss values and were therefore coded as having %100 ml blood loss for (P-)POSSUM analysis. No other (P-)POSSUM variables were missing. Patients in the OIR group were more likely to be operated on by a trainee; in all but one case trainees were directly supervised by a consultant.

4 Is Routine ICU Necessary after Elective Open Aortic Surgery? 255 Table 1. Patient demographics and co-morbidities OIR (nz152) Elective ICU (nz26) P value Median age, years (IQR) 72 (66 77) 71 (66 76) 0.53 Males, n (%) 134 (88) 22 (85) 0.53 Regular smoker within 6 months of operation, 57 (38) 8 (31) 0.52 n (%) * History of diabetes, n (%) 12 (8) 3 (12) 0.46 History of hypertension, n (%) 73 (48) 18 (69) 0.06 History of angina, n (%) 23 (15) 11 (42)!0.01 History of myocardial infarction, n (%) 22 (14) 8 (31) 0.05 Left ventricular function on echocardiography, 30:6:1 9:7:3!0.01 good:moderate:poor NYHA score frequencies, 1:2:3:4 99:46:3:0 11:11:4:0!0.01 Renal impairment, n (%) 39 (26) 8 (31) 0.63 Median AAA diameter, cm (IQR) 6.0 ( ) 6.9 ( ) 0.01 ASA score frequencies, 1:2:3:4 3:67:72:1 0:5:18: Median POSSUM physiology score (IQR) 18 (16 22) 21.5 (18 27)!0.01 AAA, abdominal aortic aneurysm; ASA, American Society of Anesthesiologists; ICU, intensive care unit; IQR, interquartile range; OIR, overnight intensive recovery; NYHA, New York Heart Association; POSSUM, physiological and operative severity score for the enumeration of mortality and morbidity. * Missing data: one OIR group. Missing data: four OIR group. Defined as serum creatinine O125 mmol/l. Outcomes There were no significant differences in postoperative length-of-stay, in-hospital morbidity or mortality between the two groups (Table 3). Patients in the OIR group had a significantly shorter mean ICU stay. Ten patients (7%) in the OIR group were admitted to ICU within 48 h of surgery: three required fluid resuscitation and ventilatory support, two after relaparotomy for bleeding, two for management of hypotension, two for rhabdomyolysis treatment protocols, and one patient was admitted for management of fluid overload. No patient in the OIR group was admitted to ICU directly from theatre. A further eight patients were admitted to ICU more than 48 h postoperatively: the commonest indication was sepsis or respiratory failure. In the elective ICU group, 15 of the 26 patients required only 1 day on ICU. For all patients, mean postoperative hospital stay before discharge or death was 13 (16) days. Overall, fewer than predicted patients experienced one or more complications (observed 101 versus predicted morbidity 95% CI ). There was no significant difference between the observed and predicted morbidity for either the OIR or elective ICU groups (OIR group observed 85 versus predicted 95% CI ; ICU group observed 16 versus predicted 95% CI 15 23). Chest infections, postoperative supraventricular tachycardias, cardiac failure, and impaired renal function were the most common complications (Table 4). Haemorrhage from the operative site requiring re-operation was more common in the ICU group (pz0.02), otherwise there were no significant differences in individual complication rates between the two groups (data not shown). The total number of postoperative complications was 197. Overall, in-hospital mortality was 2% (3/178). The causes of death were acute respiratory distress syndrome, acute left ventricular failure, and acute myocardial infarction. There were fewer deaths than predicted in the OIR group (observed 2 versus predicted 95% CI 5 17) but not in the ICU group Table 2. Aortic surgery performed Operation performed OIR, n (%) Elective ICU, n (%) Infrarenal AAA repair 120 (79) 18 (69) Infrarenal aortic bypass for AOD 18 (12) 1 (4) Juxtarenal * AAA repair 6 (4) 4 (15) Infrarenal aortic endarterectomy for AOD 3 (2) 0 (0) Infrarenal AAA repaircfemoro-popliteal arterial bypass 2 (1) 1 (4) Suprarenal AAA repair 2 (1) 0 (0) Infrarenal AAA repaircradical nephrectomy 0 (0) 1 (4) Re-do infrarenal AAA repair 1 (1) 0 (0) Suprarenal aortic endarterectomycinfrarenal aortic bypass for AOD 0 (0) 1 (4) AOD, aortic occlusive disease. * Aortic cross-clamp at or superior to the origins of one or more renal arteries but with the proximal graft anastomosis inferior to these origins.

5 256 C. J. Callaghan et al. Table 3. Operative characteristics and postoperative outcomes Procedure OIR (nz152) Elective ICU (nz26) P value Performed by trainee, n (%) 51 (34) 2 (8)!0.01 Median operative time, mins (IQR) * 175 ( ) 205 ( ) 0.02 Median blood loss, ml (IQR) 1500 ( ) 2500 ( ) 0.01 Median POSSUM operative severity 20 (16 20) 20 (16 20) 0.11 score (IQR) Mean ICU stay, days (SD) 1 (7) 5 (8) 0.02 Mean postoperative stay, days (SD) 12 (16) 16 (15) 0.30 Inhospital morbidity, n (%) 85 (56) 16 (62) 0.67 Inhospital mortality, n (%) 2 (1) 1 (4) 0.38 SD, standard deviation. * Time taken from knife-to-skin to the application of wound dressings. Missing data: 21 OIR group, three elective ICU group. (observed 1 versus predicted 95% CI 1 7). Overall, fewer than predicted patients died (observed mortality 3 versus predicted mortality 95% CI 8 21). Discussion Using (P-)POSSUM equations, we show that the overwhelming majority of patients undergoing elective open aortic surgery can be managed overnight in an intensive recovery area without excess mortality or morbidity. This finding has significant implications, as ICU is used routinely after aortic surgery in 85% of UK district general hospitals and 59% of teaching hospitals. 1 Groups from the US have shown that patients having elective open infrarenal aortic surgery can be managed without routine postoperative ICU Table 4. Common postoperative complications Complication OIR, n (%) Chest infection * 35 (23) 4 (15) New-onset supraventricular 18 (12) 2 (8) tachycardia Cardiac failure * 12 (8) 4 (15) Impaired renal function * 10 (7) 5 (19) Acute confusional state 13 (9) 1 (4) Pyrexia of unknown origin * 8 (5) 3 (12) Wound infection * 7 (5) 1 (4) Haemorrhage, site other than 7 (5) 0 (0) operative site * Respiratory failure requiring 5 (3) 1 (4) emergency ventilation * Prolonged ileus 6 (4) 0 (4) Infection, site other than chest, 5 (3) 1 (4) urinary tract or wound * Haemorrhage from operative 2 (1) 3 (12) site requiring re-operation * Thrombosis (or embolus) other than DVT or PE 5 (3) 0 (0) Elective ICU, n (%) DVT, deep vein thrombosis; PE, pulmonary embolism. Only complications occurring on more than four occasions during the study period are included. * POSSUM definition. admission. However, these studies have either been small, 4 or have utilised ICU in a larger proportion of patients. 3 Podore and Throop described a policy whereby 50 consecutive patients were observed in the theatre recovery area for a minimum of 3 h before transferring either to a surgical ward or ICU. Six patients (12%) were admitted to ICU and no patient admitted directly to the ward needed subsequent ICU admission. There were no deaths in either group, but morbidity was not reported. Bertges et al. reported on the gradual introduction of a pathway by which patients having elective open infrarenal AAA repair were admitted either to ICU directly from theatre or to the ward after observation in theatre recovery. In total, 69 out of 314 patients were managed using the latter approach. In this group, one patient required transfer to ICU. After full pathway implementation, 53 of 83 patients (64%) were transferred straight to the ward. Overall mortality was 1.9% (6/314), and major complications were significantly lower in the group managed on the ward postoperatively. These studies differ from our report in three ways. Firstly, both studies excluded patients undergoing suprarenal aortic surgery and those having concomitant major intraabdominal surgery such as nephrectomy. Bertges et al. did not include patients having operations for AOD, another high-risk group. 12 These may be contributing factors to their low rates of ICU admission in patients admitted directly to the ward. Secondly, the decision to admit to ICU was made either at the conclusion of the operation 3 or after observation in the theatre recovery area. 4 In both cases, this implies that an ICU bed would need to be kept available for the majority of the day, thus partially negating the advantages of a non-icu pathway. Thirdly, neither study used risk stratification equations to generate expected morbidity and mortality rates. Outside of a randomised trial or a comparison with historical data, it is otherwise difficult to be certain that selective ICU use does not

6 Is Routine ICU Necessary after Elective Open Aortic Surgery? 257 result in excess morbidity or mortality. However, in these two papers no deaths were reported in patients discharged directly to the ward. Patients suitable for OIR can be selected preoperatively using only clinical findings combined with readily available investigations. As expected, the patients in the elective ICU group had higher rates of symptomatic ischaemic heart disease, poor left ventricular function, and higher NYHA, ASA, and POSSUM physiology scores. The validity of our preoperative assessment of surgical difficulty was confirmed by the findings of longer surgery and higher intraoperative blood loss in patients chosen for elective ICU care. This occurred despite having trainees perform a high proportion of the operations on patients in the OIR group. Postoperative stay in the OIR group was not lengthened, as overall mean stay was similar to that reported in the large MASS trial 13 (13 days versus 13.8 days). The success of the OIR pathway depends upon accurate preoperative identification of low-risk patients, as well as surgical, anaesthetic, and nursing expertise. Our indications for OIR suitability do not specify rigid physiological parameters, allowing clinical judgement to take precedence. This necessitates acceptance of a learning curve and the obligation to regularly audit outcomes. The learning curve is ongoing, as seen by the finding that the majority of patients receiving elective ICU care stayed only one day, and may not have required this level of care. The presence of co-morbidities, particularly of the cardiorespiratory systems, plays a greater role in determining the appropriateness of using OIR than the type of aortic surgery required. For example, suprarenal AAA repair is not a contraindication to OIR in a fit patient. Anaesthetic techniques are critical to the success of the OIR pathway. Careful attention to intraoperative fluid balance, active warming techniques, and the routine use of epidural analgesia and ultra-short acting anaesthetic agents are necessary to facilitate extubation in theatre. 14,15 A prospective, randomised trial has shown that extubation in theatre after elective open infrarenal AAA repair is safe. 2 In this trial all patients were admitted to ICU postoperatively, however, the authors recognised that this would probably be unnecessary in patients having uncomplicated surgery. The major limitation of our study is its retrospective nature. This makes morbidity data collection difficult, but should have little or no effect on the gathering of in-hospital mortality data. Three patients were excluded due to missing case notes, although there was no inpatient mortality in this group. A further limitation is that it is difficult to be sure that using the OIR pathway decreases total ICU use, as it is possible that inappropriate use of OIR leads to emergency ICU admission due to postoperative complications. However, only 31% (82/267 days) of the total ICU stay in the OIR group came from patients admitted within 48 h of surgery. It seems unlikely that admitting a patient to ICU immediately after surgery would prevent a complication developing more than 48 h later. Although a cost-analysis was not undertaken, strategies that reduce ICU-usage without increased morbidity or mortality would be expected to achieve cost-savings, as approximately one-third of the cost of an elective open AAA repair is made up of ICU-related expenditures. 13 Admission to ICU for 1 day after elective open infrarenal AAA repair increases hospital charges by 21%. 3 An additional benefit of decreasing ICU use would be a reduction in cancelled operations due to lack of ICU beds. The value of a non-icu pathway may be increased if AAA screening is introduced, as men with screening-detected aneurysms are younger and have fewer co-morbidities, 16 thus requiring less intensive monitoring postoperatively. Even with the introduction of endovascular aneurysm repair, younger patients may still need to undergo open repair due to reservations about the long-term reliability of endovascular stents. 17 This retrospective study shows that the overwhelming majority of patients can be preoperatively selected to undergo elective open aortic surgery without routine ICU care. This includes those requiring suprarenal AAA repair and operations for AOD. Selection is based on clinical criteria and readily available investigations. Standard surgical techniques, combined with epidural anaesthesia, active warming, and the use of short-acting anaesthetic drugs, allow extubation in theatre and overnight management in theatre recovery before transfer to a surgical ward. This has been achieved without excess morbidity or mortality and with an ICU admission rate of 7% within 48 h of surgery. Acknowledgements We would like to thank Dr Ian Munday for his anaesthetic expertise, Mrs Sylvia Cartwright and Miss Karen Munns for their secretarial assistance and Mr Neil Osborne for helping with the theatre database. The Centre for Applied Medical Statistics is supported by NHS Executive Eastern. There are no conflicts of interest.

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